The present invention relates generally to electro-optical couplers, and more particularly, to various electro-optical packages that facilitate the coupling of optical cables to printed circuit boards.
With advances in optical technologies, such as Wave Division Multiplexing (WDM), more and more computer and communication networks are being built using fiber optic cables. With WDM for example, multiple optical signals, each at different wavelengths, are used to simultaneously transmit multiple communication channels across a single optical fiber. To further increase bandwidth, multiple fibers may also be employed. While fiber optics have significantly increased the broadband capabilities of communication networks, much of the signal processing at nodes of the network is still performed in the electrical domain using integrated circuits. Thus electro-optical couplers, which convert optical signals into electrical signals and vice versa, have been used at the interface between the optical cables and the nodes.
A typical electro-optical coupler includes a connector for receiving an optical fiber and a housing which houses a photonic device. The photonic device is usually mounted onto a substrate. A ferrule included in the housing is used to align the optical fiber with the photonic device. Electrical traces and contacts provided on the substrate are used to electrically connect the coupler to the outside world, typically a printed circuit board. One of the major hurdles in manufacturing these electro-optical couplers is the proper alignment the fiber to the optically sensitive components on the opto-electric (i.e., photonic) device. Also during solder reflow to attach the coupler to the printed circuit board, it is possible for the photonic device to become mis-aligned with the fiber due to mismatches of thermal expansion of the materials used to hold the fiber and the photonic device in place. Contamination at the termination of the fiber the coupler may also occur during mounting onto a printed circuit board. See for example, xe2x80x9cIntegrated Fiber Optic Transmitters and Receivers for SONET/ATM Applications,xe2x80x9d, T. Muoi, Electronics Components and Technology Conference 1995 Proceedings, p. 1092.
Another type of connector for high density applications involves the use of a substrate that is etched to provide grooves to accommodate multiple fibers. See for example, Silicon Waferboard Based Single Mode Optical Fiber Interconnects,xe2x80x9d P. Haugsjaa, G. Duchene, J. Mehr, A. Negri And M. Tabasky, IEEE Transactions On Components, Packaging and Manufacturing Technologyxe2x80x94Part B, Vol. 19, No. 1, Feburary 1996. With this type of connector, multiple devices, typically either transmitters or receivers, are mounted onto the substrate. The grooves are used to align the individual fibers with either the photo-transmitting or receiving regions on the devices. Separate bond pads coupled to each of the devices are also provided on the substrate to couple the devices to external components, such as another chip or a printed circuit board. While this type of connector is useful for high density applications, they are expensive to produce and lack the reliability required in order to provide a reliable xe2x80x9clast-milexe2x80x9d optical interconnect to the end user.
In general, current connection methods are typically designed around plug-in connections along the optical pathway. This means that low reliability optical components on the board side of the connector must be able to survive electronics soldering environments without contamination to sensitive optical surfaces. Additionally, the requirement on optical alignment are orders of magnitude more restrictive than those for plug-in electrical connections.
Electro-optical packages that embed the electronics of the packages directly to the optical cabling, provide short electrical connection paths for high performance, and that provide a robust interconnect are therefore needed.
To achieve the foregoing, and in accordance with the purpose of the present invention, electro-optical packages that facilitate the coupling of optical cables to printed circuit boards are disclosed. A first electro-optical package includes an integrated circuit and a connector sleeve configured to receive a plug-in optical assembly. The plug-in optical assembly includes a backing piece and an opto-electric device mounted onto the backing piece. An electrical connection is provided between the opto-electric device and a contact location on the backing piece and a contact is provided between the contact location on the backing piece and the integrated circuit. The connector sleeve of first electro-optical package enables the optical assembly to be xe2x80x9cpluggedxe2x80x9d into the package. The plug-in fiber optic assembly provides a number of advantages, including the easy removal for inspection or replacement of the assembly, and protection from contaminants during board population and assembly. With a second electro-optical package, an integrated circuit having an active surface facing in a first direction and an opto-electric device having contact points facing a second direction are provided. The integrated circuit and the opto-electric device are positioned with respect to one another such that a direct electrical connection can be formed between the active surface of the integrated circuit and the contact points of the opto-electrical device. This second embodiment thus provides an extremely short electrical signal paths between the integrated circuit and the opto-electric device.